Architecture

OxideBBS is a Rust modular monolith. It ships as one primary server binary with small internal crates for focused boundaries.

Telnet Listener
    |
Transport
    |
Session
    |
Menu / Command Router
    |
Core Services
    |
DecentDB Repository Layer

Door execution follows a separate path:

Session
    |
Door Service
    |
Node Manager
    |
Drop File Writer
    |
Door Runner
    |
DOSEMU2 Runtime
    |
PTY/COM1 Bridge

Constraints

• Use Rust.
• Use DecentDB as the only system database.
• Keep telnet as the default caller path. Physical serial/modem support remains disabled by default and should be enabled only by sysops who intentionally configure it.
• Treat ANSI/CP437 as a first-class byte-oriented terminal format.
• Do not use Ratatui for the remote caller UI.
• Keep door execution isolated from core session logic.
• Do not bundle copyrighted or abandonware DOS doors.

Terminal Profiles

The remote caller UI must support both 80-column and 40-column terminal profiles. Menus, prompts, status bars, wrapping, paging, and ANSI assets should fit the active terminal width without corrupting CP437 art or truncating commands.

Profile	Caller target	Width	ANSI	Charset behavior
ansi80	BBS/ANSI clients such as SyncTERM	80	Yes	CP437
plain	Generic telnet clients	80	No	ASCII
c64	C64, C64 Ultimate, and C64 terminal apps	40	No by default	PETSCII-friendly ASCII fallback

The c64 profile is for callers connecting from Commodore-compatible terminal software. OxideBBS is not ported to run on C64 hardware.

Menus

Menus are configured as safe key-to-action mappings. Screen assets draw the visual menu, while menu entries decide what a pressed key does. For sysops, this means ANSI art can change without changing command behavior, and command routing can change without editing art files.

Door byte bridge model

Door launch is separated from caller transport logic.

caller telnet client
  <-> OxideBBS caller transport
  <-> OxideBBS PTY byte bridge
  <-> DOSEMU2 COM1 pts backend
  <-> DOSEMU2-emulated COM1 UART
  <-> DOS door program

OxideBBS owns Transport and bridge ownership during door sessions. DOSEMU2 remains an isolated runtime that receives caller bytes over a host PTY file and presents them as COM1 UART bytes. This is not a Rust-hosted FOSSIL driver. A DOS-side FOSSIL TSR may be loaded by a specific door if that door requires FOSSIL APIs.